Hi, I have a GK MBE212 and while playing last night I noticed a fart sound coming from the lower speaker. I replaced all cables and tried my bass in another amp so it points to the cab. I took the bottom speaker out but I can't see any obvious damage. Can anyone suggest anything to try, before having to cough up some cash to replace the speaker? Also, are there any cheaper decent alternatives to the Paragon 12", 300W, 8 Ohm, Neodymium Bass Driver it has by default. Any help is much appreciated. Cheers!